Images of Comet Wild 2 eBook

Findings from a historic encounter between NASA’s
Stardust spacecraft and a comet have revealed a much
stranger world than previously believed. The
comet’s rigid surface, dotted with towering
pinnacles, plunging craters, steep cliffs, and dozens
of jets spewing violently, has surprised scientists.

Image above: This image and diagram show the
comet Wild 2, which NASA’s Stardust spacecraft
flew by on Jan. 2, 2004. The picture on the
left is the closest short exposure of the comet.
The listed names on the right are those used by the
Stardust team to identify features. “Basin”
does not imply an impact origin.

Animation: This movie strings together a series
of still images of comet Wild 2 taken during Stardust’s
historic flyby of the comet. Animation credit:
NASA/jpl-Caltech.

“We thought Comet Wild 2 would be like a dirty,
black, fluffy snowball,” said Stardust Principal
Investigator Dr. Donald Brownlee of the University
of Washington, Seattle. “Instead, it was
mind-boggling to see the diverse landscape in the first
pictures from Stardust, including spires, pits and
craters, which must be supported by a cohesive surface.”

“We know Wild 2 has features sculpted by many
processes. It may turn out to be typical of
other comets, but it is unlike any other type of
solar system body,” Brownlee said. He is
lead author of one of four Stardust papers appearing
in the Fri., June 18, issue of Science. “We’re
fortunate that nature gave us such a rich object
to study.”

Stardust images show pinnacles 100 meters tall (328
feet), and craters more than 150 meters deep (492
feet). Some craters have a round central pit
surrounded by ragged, ejected material, while others
have a flat floor and straight sides. The diameter
of one large crater, called Left Foot, is one fifth
of the surface of the comet. Left Foot is one
kilometer (.62 miles) across, while the entire comet
is only five kilometers (3.1 miles) across.

“Another big surprise was the abundance and
behavior of jets of particles shooting up from the
comet’s surface. We expected a couple
of jets, but saw more than two dozen in the brief
flyby,” said Dr. Benton Clark, chief scientist
of space exploration systems, Lockheed Martin Space
Systems, Denver.

The team predicted the jets would shoot up for a short
distance, and then be dispersed into a halo around
Wild 2. Instead, some super-speedy jets remained
intact, like blasts of water from a powerful garden
hose. This phenomenon created quite a wild ride
for Stardust during the encounter.

“Stardust was absolutely pummeled. It flew
through three huge jets that bombarded the spacecraft
with about a million particles per second,”
said Thomas Duxbury, Stardust project manager at
NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Twelve particles, some larger than a bullet, penetrated
the top layer of the spacecraft’s protective
shield.